2010 Census: More than a half-million same-sex unmarried households in United States

On the topic of families, the number of married couples with children dropped about 5.7 percent to 23.4 million, or roughly 20 percent of U.S. households. That's down from a share of 23.5 percent in 2000 and 43 percent in 1960.

The decreases in traditional families were seen in 42 states plus the District of Columbia, while the remaining eight - Nevada, Utah, Idaho, Arizona, Colorado, Texas, North Carolina and Georgia - saw increases. Those eight states generally have a higher number of either immigrants or Mormon residents.

In contrast, non-family households made up of single people such as seniors living alone, or opposite-sex or same-sex partners without children, jumped 13 percent to roughly 38 million. Married couples with no kids, which include younger couples and older empty-nesters, rose 9 percent to more than 32 million.

"In American politics, there's a nostalgia element when invoking terms such as 'family values.' But that term is out of touch with the way many Americans live, given demographic changes such as gay marriage" and cohabitation, said Julian E. Zelizer, a professor of history and public affairs at Princeton University.

Preliminary census numbers show that unmarried partners made up 6.5 million, or nearly 6 percent of U.S. households. Those figures include roughly 581,300, or a half-percent of households, composed of same-sex unmarried couples. Measured by shares, the District of Columbia ranked highest for same-sex unmarried households at 2 percent.

Official 2010 data on unmarried partner households will be released beginning in June, followed by figures on same-sex spouses in November.